This invention relates to a navigational aid which can be used, for example, to assist in the navigation of craft such as boats or aircraft.
Navigation of boats and aircraft is usually accomplished with the aid of maps or charts, together with instruments which may include rules, compasses and calculators. Navigation with such instruments requires a reasonable degree of skill and errors are easily made. If it is required to calculate the position of the craft accurately, taking into account, for example, the effect of wind, altitude, temperature, pressure and effects such as the "chord defect", the calculations may become highly complicated and laborious, with an increased possibility of error.
One device which has been proposed in an attempt to overcome the chord defect, which arises due to the fact that an aircraft follows a curved path relative to the surface of the earth, whereas the distance between points on a map is measured on a flat surface, is described in U.S. Pat. No. 4,555,852 to Brazel. This patent describes a hand-held compass which has legs which are interconnected by a mechanism which compensates for the chord defect. This device does not, however, address the other problems referred to above.